Numerous machines have been developed for finishing the valve seats on an engine block, which machines grind or cut the valve seat to permit a conventional valve to be sealingly seated thereon. These known machines have normally provided a movable table such as a cross-slide arrangement, for permitting positioning of the engine block below the seat finishing tool. For accurate positioning of the engine block below the finishing tool, control structure in the form of limit switches and the like have been required. Even still, the required machining tolerances still fall far short of those desired in order to permit the valve seat to be concentrically related to the valve stem bore as formed in the engine block.
To improve upon the finishing tolerances of the valve seat, several machines have been proposed which permit the finishing tool to be angularly and/or laterally moved a limited extent so as to provide for more accurate finishing of the valve seat. Since most engine blocks are cast and are thus subject to substantial dimensional variations, the problem of accurately aligning and finishing the valve seat relative to the bore is thus a longstanding problem. While the known machines have been able to attain fairly good dimensional tolerances, nevertheless there is a long felt need with respect to even further improving or minimizing these tolerances so as to provide for more efficient engine performance and less wear and burning of the valve and valve seat.
One known machine which has attempted to compensate for these inaccuracies is disclosed in U.S. Pat. No. 3,443,399 (Pope et al.) The Pope et al. apparatus provides a rotatable finishing tool supported on an elongated spindle arrangement which possesses a pair of axially spaced universal joints to permit the tool to be misaligned both angularly and laterally through a limited extent. However, the structure of Pope et al. is unduly complex due to the necessity of utilizing a pair of axially spaced universal joints. Further, all of the pushing force as applied to the tool must be transmitted directly through these universal joints, which thereby greatly increases the wear of the joints. Further, the machine of Pope et al. does not have any capability of fixedly locking the tool in a desired angular and/or lateral offset position so as to insure that the tool will remain in this position during the finishing operation.
Another known machine, as disclosed in U.S. Pat. No. 2,116,498 issued to Hall, possesses substantially the same disadvantages as that of Pope et al.
Accordingly, it is an object of the present invention to provide an improved machine for finishing valve seats on an engine block, which machine overcomes the above-mentioned disadvantages and permits efficient finishing of valve seats with a higher degree of accuracy.
A further object is to provide a machine, as aforesaid, which permits the finishing tool to readily adjust for both angular and lateral misalignment of the bore formed in the engine block, and which permits the finishing tool to be locked in its adjusted position whereby it is substantially aligned with the bore in the engine block even though the tool may be both angularly and laterally misaligned relative to its own driving axis, so that the finished valve seat can thus be machined with a much smaller tolerance than previously obtainable.
Still a further object is to provide a machine, as aforesaid, which uses a joint possessing universal movement but which is constructed in such a manner as to readily permit the transfer of the necessary axial pushing force to the finishing tool without causing unnecessary wear of the joint structure.
Another object is to provide a machine, as aforesaid, which employs an independently and separately movable pilot which can be axially extended into the valve bore to insure that the tool assumes the desired angularly and/or laterally offset position so as to be properly aligned with the bore in the valve housing, which pilot can be pressed into the bore independently of the rotatable structure used for driving the tool.
It is also an object to provide an improved machine, as aforesaid, which is desirable for use with engine blocks having several bores formed therein so as to permit the individual tools to be accurately aligned with the respective bores while permitting the simultaneous finishing of valve seats associated with several bores.
Another object is to provide an improved machine, as aforesaid, which is simple and dependable in operation and requires a minimum of maintenance.
Still another object is to provide an improved pilot rod adapted for insertion into the valve stem bore for permitting proper seating of the finishing tool on the rough valve seat.
Other objects and purposes of the invention will be apparent to persons familiar with machines of this general type upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, the words "upwardly", "downwardly", "leftwardly" and "rightwardly" will refer to directions in the drawings to which reference is made. The words "inwardly" and "outwardly" will refer to directions toward and way from, respectively, the geometric center of the machine and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.